Variability of f_o E in Relation to the Solar Indices (R_z and F_(10.7) ) at the Equatorial Ionosphere (Ouagadougou Station)

The correlation coefficients between the critical frequency of the ionosphere E-layer ( foE )and the solar radio flux have not been formally evaluated at the Ouagadougou station. The purpose of this paper is to conduct a study on the variability of the critical frequency of ionosphere E-layer with the solar radio flux (F10.7) and sunspot number (Rz) at the Ouagadougou station. The Ouagadougou station is located at the equatorial ionosphere whose coordinates are: lat: 12.5°N; long: 358.5°E; dip 1.5. Moreover, the local time is equal to the universal time (LT=UT). We worked on the solar cycles 21 and 22 (SC21 and SC22) considering their different phases (minimum, increasing, maximum, and decreasing). The values of foE taken into account are those measured at noon (12:00 LT). The results show a good correlation between foE and Rz, and between foE and F10.7. Thus, the correlation coefficient evaluated between  foE and Rz is 0.96 at SC21 and 0.93 at SC22, and between foE and F10.7 is 0.95 at SC21 and 0.93 at SC22. We subsequently compared foE of the two solar cycles for the same phase. The calculated deviation between the minimum of SC21 and SC22 is 4.46%.  We then find a very small variation of foE from a solar cycle to another at the minimum phase, and this is also verified at the other phases.